base/files/memory_mapped_file_win.cc

   1 // Copyright 2013 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #include "base/files/memory_mapped_file.h"
   6
   7 #include "base/files/file_path.h"
   8 #include "base/strings/string16.h"
   9 #include "base/threading/thread_restrictions.h"
  10
  11 namespace base {
  12
  13 MemoryMappedFile::MemoryMappedFile() : data_(NULL), length_(0), image_(false) {
  14 }
  15
  16 bool MemoryMappedFile::InitializeAsImageSection(const FilePath& file_name) {
  17   image_ = true;
  18   return Initialize(file_name);
  19 }
  20
  21 bool MemoryMappedFile::MapFileRegionToMemory(
  22     const MemoryMappedFile::Region& region) {
  23   ThreadRestrictions::AssertIOAllowed();
  24
  25   if (!file_.IsValid())
  26     return false;
  27
  28   int flags = image_ ? SEC_IMAGE | PAGE_READONLY : PAGE_READONLY;
  29
  30   file_mapping_.Set(::CreateFileMapping(file_.GetPlatformFile(), NULL,
  31                                         flags, 0, 0, NULL));
  32   if (!file_mapping_.IsValid())
  33     return false;
  34
  35   LARGE_INTEGER map_start = {};
  36   SIZE_T map_size = 0;
  37   int32 data_offset = 0;
  38
  39   if (region == MemoryMappedFile::Region::kWholeFile) {
  40     int64 file_len = file_.GetLength();
  41     if (file_len <= 0 || file_len > kint32max)
  42       return false;
  43     length_ = static_cast<size_t>(file_len);
  44   } else {
  45     // The region can be arbitrarily aligned. MapViewOfFile, instead, requires
  46     // that the start address is aligned to the VM granularity (which is
  47     // typically larger than a page size, for instance 32k).
  48     // Also, conversely to POSIX's mmap, the |map_size| doesn't have to be
  49     // aligned and must be less than or equal the mapped file size.
  50     // We map here the outer region [|aligned_start|, |aligned_start+size|]
  51     // which contains |region| and then add up the |data_offset| displacement.
  52     int64 aligned_start = 0;
  53     int64 ignored = 0;
  54     CalculateVMAlignedBoundaries(
  55         region.offset, region.size, &aligned_start, &ignored, &data_offset);
  56     int64 size = region.size + data_offset;
  57
  58     // Ensure that the casts below in the MapViewOfFile call are sane.
  59     if (aligned_start < 0 || size < 0 ||
  60         static_cast<uint64>(size) > std::numeric_limits<SIZE_T>::max()) {
  61       DLOG(ERROR) << "Region bounds are not valid for MapViewOfFile";
  62       return false;
  63     }
  64     map_start.QuadPart = aligned_start;
  65     map_size = static_cast<SIZE_T>(size);
  66     length_ = static_cast<size_t>(region.size);
  67   }
  68
  69   data_ = static_cast<uint8*>(::MapViewOfFile(file_mapping_.Get(),
  70                                               FILE_MAP_READ,
  71                                               map_start.HighPart,
  72                                               map_start.LowPart,
  73                                               map_size));
  74   if (data_ == NULL)
  75     return false;
  76   data_ += data_offset;
  77   return true;
  78 }
  79
  80 void MemoryMappedFile::CloseHandles() {
  81   if (data_)
  82     ::UnmapViewOfFile(data_);
  83   if (file_mapping_.IsValid())
  84     file_mapping_.Close();
  85   if (file_.IsValid())
  86     file_.Close();
  87
  88   data_ = NULL;
  89   length_ = 0;
  90 }
  91
  92 }  // namespace base